Many relatively large turbine engines, including turbofan engines, may use an air turbine starter (ATS) to initiate turbine engine rotation. Typically, the ATS includes at least a turbine section coupled to an output section that are each mounted within an aluminum ATS housing. The turbine section is also coupled to a high pressure fluid source, such as compressed air, and includes a turbine wheel and an output shaft. The turbine wheel has a hub with a plurality of blades extending radially therefrom. The output shaft extends axially from the hub and is coupled to the output section. Thus, when the high pressure fluid source impinges upon the turbine blades, the output shaft rotates at a relatively high rate of speed to power the turbine engine.
In many instances, the turbine blades are constructed of a high-strength material capable of withstanding the high speeds encountered during aircraft operation, such as, for example, titanium. To allow the turbine wheel to produce the maximum amount of power for optimal ATS operation and to abide by size restrictions, a reduced clearance is usually provided between the turbine blades and the ATS housing.
Although the above configuration is generally safe and effective, it may have certain drawbacks. For example, during operation, the turbine blades may rub against the housing and cause friction. During normal ATS operating conditions, such as when the ATS is operating at temperatures below 600° F., the contact between the blades and housing may not adversely affect ATS operability; however, in instances in which the fluid source temperatures exceeds 600° F., this may not be the case. In particular, the aluminum housing may lose structural integrity, which may cause inoperability of the ATS. Additionally, the turbine wheel may become displaced from its original position, and, for example, may inadvertently travel axially through the ATS, and, consequently, may damage other components of the ATS, such as a stator.
Accordingly, there is a need for an air turbine starter that is operational and capable of maintaining structural integrity at temperatures above 600° F. In addition, there is a need for an air turbine starter that is lightweight and relatively inexpensive to implement. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.